In recent years, attention to the SDN (Software-Defined Network) technology represented by OpenFlow has been increasing as a new traffic control technology. The advent of the SDN technology enables routing by units of microflows, which has been difficult with conventional networking technologies. In addition, flow measurement technologies such as NetFlow are spreading, which makes it easy to grasp detailed traffic information (flow data) by units of micro flows.
In OpenFlow, a flow is controlled by using a flow entry on an OpenFlow switch. The flow entry includes a flow identification field and an action field. The flow identification field represents conditions for a flow (for example, a packet) in terms of source and destination IP addresses, source and destination port numbers, protocol number, and the like. The action field represents a method of processing the flow that matches the conditions, such as outputting to a specific port, dropping the flow, and the like.
A flow entry that includes a wildcard in the conditions enables controlling multiple flows by the single entry. By using the flow entry including a wildcard, a flow whose traffic volume is large can be controlled by a small number of flow entries.
On the other hand, a sudden occurrence of a flow whose traffic volume is large (a spike flow) is often observed on the Internet. If such a spike flow concentrates on a specific link, congestion may occur in the link, and consequently, the performance of the entire network may drop.
To cope with a spike flow, individual control such as traffic shaping and detour control may be performed so as to prevent a performance drop of the entire network.